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Shamir Secret Sharing Dialog Guide

The Shamir Secret Sharing [GF(256)] dialog splits a secret into shares and reconstructs it from a threshold number of shares. Use the same prime value and threshold settings when splitting and joining.

Shamir Secret Sharing dialog showing share and threshold settings, prime controls, source input, share list, and joined result.

Figure 1. Shamir Secret Sharing dialog. The upper section splits a source value into shares; the lower section combines selected shares to reconstruct the value.

Screen Areas

  1. Shares — Number of shares to create. The default is 5.
  2. Threshold — Minimum number of shares required to reconstruct the secret. The default is 3.
  3. Prime — Prime value used by the sharing operation, entered as hexadecimal. The selected Bytes value sets the size for Make Prime; available choices are 8, 16, 32, 64, 128, and 256 bytes. C clears the prime. IsPrime checks whether the entered value is prime.
  4. Source — Secret value to split. Select its input representation (Hex, String, or Base64), enter the value, and select Split. C clears the source; the adjacent field shows its length.
  5. Shared — Enter a share value in hexadecimal and select Add to append it to the share list. The adjacent field displays its length.
  6. Shared value list — Shows the shares available for reconstruction. Right-click a row to copy or delete it. Clear removes all listed shares.
  7. Join — Reconstructs the original secret from the listed shares using the configured threshold and prime.
  8. Joined — Displays the reconstructed value using the selected representation (Hex, String, or Base64). C clears the result; the adjacent field shows its length.
  9. Clear Data All / Close — Clears the values and share list, or closes the dialog.

Split a Secret

  1. Set Shares to the total number of shares to generate and Threshold to the minimum number needed to reconstruct the secret.
  2. Enter a prime in Prime, or choose a byte size and select Make Prime. Use IsPrime to check a manually entered value.
  3. Enter the secret in Source and select its representation.
  4. Select Split. The generated share values appear in the list. Save or copy the shares and keep the threshold and prime information available for reconstruction.

Join Shares

  1. Enter the same Prime and Threshold used for splitting.
  2. Add share values to the Shared field one at a time, selecting Add after each. Shares must be hexadecimal values.
  3. Add at least the threshold number of shares, then select Join.
  4. Read the reconstructed secret in Joined and choose the desired output representation.

Notes

  • The prime must be greater than the source value. An insufficient prime causes the split operation to fail.
  • Reconstruction requires at least the configured threshold number of shares; the dialog also requires at least two shares in the list.
  • Duplicate shares are rejected when adding them. Use the share list's right-click menu to copy or remove a share.
  • Shares and the original secret are sensitive. Store shares separately and clear the dialog when finished.